Balancing rotating element



Aug. 24, 1943. "c. F. SALTZ BALANCING ROTATING ELEMENT Original FiledMarch 5, 1941 Y INVENTOR. CLARE F. SALTZ H/ 8 ATTORNEY Patented Aug. 24,1943 warren smras ATEN'i orrica Divided and this application February 9,1942, Serial No. 430,009

element at a speed sufficient to cause it to select d Claims.

My invention pertains to an improved method of and means for preparingrotating elements of metal or other material for balanced rotation, andthis application is a division of my co-pending application, Serial No.381,849 filed March 5, 1941.

In the production of rotatable machine parts such as flywheels, crankshafts, and the like, it is very important to provide a uniformdistribution of the mass around the axis of rotation in order to obtaina balance as nearly perfect as possible in the rotating element. This isespecially important in the production of parts to be rotated at highspeeds. As is well known, unbalanced machine parts rotating at highspeed in fixed bearings absorb a large amount of energy and also causewear and vibration. Also, when the unbalance is considerable, it issometimes necessary to change the operating speed to some other speedless suitable for the operation desired. Such unbalance exists when thecenter of gravity of the rotating part does not coincide with the axisof rotation. But the careful balancing of such parts requires theexpenditure of considerable skill and time which adds greatly to thecost of production of such elements.

It has been customary to carefully test the element to determine onwhich side of the axis it is overbalanced and the magnitude thereof. An

attempt is then generally made to remove or to addsufficient metal at aproper location on the element to balance it. This is usually done by acut-and-try method successively testing the part and removing metaltherefrom. I am also aware that various arrangements have beenpreviously provided for automatically removing metal from such anelement to balance it in an attempt to simplify this difficult andcostly operation.

In accordance with my present invention, ma

terial is not removed from the element for the purpose of balancing butinstead the element is prepared for balanced rotation by removing onlysufficient material to form bearing surfaces so located on the elementthat when the element is mounted to rotate thereon it is balanced to thedesired degree of perfection.

It is accordingly an object of my invention to provide an improvedmethod of and means for balancing a rotating element by removing fromthe element, while it isrotating, only sufficient metal to form thbearing surfaces for balanced rotation.

It is also an object of my invention to provide an improved method ofand means for balancing a rotating element by mounting for free spinningrotation the element to be balanced, rotating the its axis of rotationand describe a surface of revolution, and then forming bearing surfaceson the portions of the element which are to be iournalled I by removingmetal therefrom at the points of coincidence of the actual surface ofthe element with,

the surface of revolution so that bearing surfaces are formed concentricwith the self-selected axis of rotation of the rotating element,eliminating the necessity for balancing the element.

Also it is a further object of my invention to provide improvedapparatus for balancing a rotating element, in accordance with myimproved method, comprising free bearing means for rotatively supportingthe lower portion of the element and means for applying driving torqueto rotate the element and keep it spinning, while metal removing meansengages it.

Further objects and advantages are within the scope of my invention,such as relate to the arrangement, operation and function of the relatedelements of the structure, to various details of construction and tocombinations of parts, elements per se, and to economies of manufactureand numerous other features as will be apparent from a consideration ofthe specification in conjunction with the drawing disclosing specificembodiments of my invention, similar reference characters being appliedto corresponding elements throughout, and in which:

Fig. 1 is a side elevational view, partially sectioned, showing myapparatus for preparing a ro-' tating element for balanced rotation;

Fig. 2 is an enlarged fragmentary sectional view taken on line- 2--2 inFig. 1, showing how the brackets of the motorized grinders are slidablymounted; and

Fig. 3is an enlarged fragmentary sectional view on line 33 of Fig. 1,showing the free bearing support.

Referring more specifically to Fig. 1 of the drawing, I haveillustratively disclosed an embodiment of my apparatus arranged forpreparing for balanced rotation at work piece or element 65 which mayconsist of a shaft 6'! having a flywheel 69 secured thereon and having aflange H projecting laterally from the lower end for some such purposeas attachment to a machine, or for limiting the axial movement of theshaft after the eleelement to be balanced may take various other forms,such as a rotor for electrical apparatus or a rotor for a turbine, forexample.

The apparatus comprises a bearing standard I3 rising from a base I5whereon the apparatus is constructed or assembled. The lower end of theelement 65 rests and spins freely upon the upper end of the bearingstandard I3 and, to provide a free bearing support, friction reducingball bearings 11 are preferably provided thereon to reduce the frictionto a minimum. The frictionreducing balls are confined in a ball-retainercage I9, in a well-known arrangement, there being several ball-bearingassemblies on the markct which are suitable for this purpose.

To spin the element so that it will select a centroidal axis about whichbalanced rotation will be obtained, any suitable source of power may beutilized, such as an electric motor 8| having suitable speed adjustablecharacteristics. The motor is mounted on the base 15, and to applydriving torque to the lower end of the vertically disposed element shaft61, a friction drive Wheel 33 is provided. This friction drive wheel 83is secured on a horizontally disposed shaft 85 which is secured to theextended end of the motor shaft through a flexible coupling 81 which maybe of any well-known construction. The friction drive wheel 83 ismaintained in positive engagement with the flange of the element bymeans of a floating bearing 89 thereon drawn upwardly by a spring 9Isuspended from a structural member 93. The friction drive wheel 83 ispreferably provided with a periphery which is either rounded or bevelledto present a minimum localized contact area engaging the lower end ofthe element.

Flange II on the lower end of the shaft 61 is enclosed in a guideaperture 95 in the structural member 93, the latter being horizontallysupported between a pair of vertical side members 95, which may beeither spaced brackets in a substantially H formation or side walls of acylindrical housing. The guide aperture 95 is of a substantially largerdiameter than the circular flange disk II and serves toapproximatelypredetermine the position of the lower end of the shaft 6'! on the freebearing standard I3 while permitting it to rotate freely to select itsown centroidal axis of rotation for balanced rotation.

The upper end of the. shaft 67 of the element is also similarly confinedwithin predetermined limits in a guide aperture 99 in a horizontal topbracket I0 I. The top bracket IUI is secured horizontally across the topof the side members 91 as by crews I93 in. the ends of these members.The guide aperture 99 is of a larger diameter than the shaft 61 topermit it to move freely therein.

Direct engagement or striking between the shaft 61 and the side walls ofthe apertures is preferably prevented by projecting streams of air orother fluid thereinto from all sides. This is conveniently provided foras by cutting in the top surface of the top bracket IN a plurality ofslots I05 extending radially and opening through the side walls towardthe center of the aperture 99, Clamped firmly on top of the top bracketIn! by means of screws I0! is a manifold plate or ring I 09 of anannular conformation having a central aperture I II in alignment withthe guide aperture 99. An annular fluid conducting inlet passage H3 inthe under side of the manifold plate I09 connects with all the radialslots I05 andsupplies the air or other fluid thereto from any suitablepressure source, to which it may be connected through a nipple H5 andhose III. A tight-sealed joint may be conveniently provided between themanifold ring I09 and the topbracket IDI by inserting any suitablegasket material therebetween, as will be understood.

When the upper end of the shaft 61 of the spinning element approachesthe side wall of the guide aperture 99 in any direction, the cylindricalperipheral surface of the shaft closely approaches the side wall of theaperture tending to confine or restrict the jets of fluid from anadjacent one of the slots I 05 and this applies a force gently guidingthe shaft away from the side wall of the aperture. If the shape of thework pieces makes it desirable, the lower guide aperture may also besimilarly provided with slots for projecting fluid toward the rotatingelement, although this may be omitted when the lower end of the motordriven work piece has a. flange II, as shown.

As the unbalanced element spins, it rotates on its self-selectedcentroidal axis about which balanced rotation is obtained, and itdescribes a surface of revolution larger in diameter than the shaft, inaccordance with the amount of unbalanced mass in the element.

All masses under rotation seek to revolve upon an axis passing throughthe center of mass of the element, but with an unbalanced memberrotating on flxed bearings this condition is not attainable so that thestate of unbalance continues, causing vibration, power loss and wear. Inaccordance with my invention the element being prepared for balancedrotation is free to shift and select its own axis of rotation, which itdoes, and the element then rotates on an axis passing through the centerof gravity. This selfselected axis of rotation, which I have termed thecentroidal axis, is displaced from the geometrical axis by an amountcorresponding to the amount of unbalanced mass in the body beingbalanced, as more fully described in my copending parent patentapplication.

In Fig. 1, the element is shown in full lines in its extreme right-handposition and a dotted line represents its extreme left-hand position.New bearing surfaces are cut simultaneously upon all portions of theshaft which are to be journalled. This is accomplished by approachingthe shaft 61 with any suitable metal removing devices, such as rotatinggrinding'wheels H9 supported and driven by electric motors I2I mountedon the ends of bars I23 which slide through apertures I25 in the sidemember 91.

The sliding motor-supporting bars I23 and the apertures I25 are of asquare, or other noncircular cross section, as shown in Fig. 2, so thatthe shafts of the motors are maintained disposed in suitable vertical orpredetermined positions I while being moved toward or away from therotating element. A handle I21 may be provided connected to the twoslidable brackets I23 for conveniently moving both of the grindingwheels H9 against the work. As the grinding wheels H9 are at first movedinto engagement with the shaft 61, a brief contact is established on eduring each revolution. As the metal is cut away to form the new bearingsurfaces, the period of contact between the grinding wheels and theshaft becomes longer until finally a smooth but light contact ismaintained during the entire rotation. This informs the operator thatthe operation is completed and that new bearing surfaces have been outwhich are concentric with the centroidal axis. Bearing surfaces of anydesired length may be cut by selecting grind-- ing wheels H9 of acorresponding axial dimension. Various elements, or work pieces, ,may bethe grinding wheels exert but very slight re' tarding forces onthe'rotating element or these wheels may actually be rotated in the samedirection but at a higher speed.

It is apparent that within the scope of the invention, modifications anddifferent arrangements may be made other than herein disclosed, and thepresent disclosure is illustrative merely, the invention comprehendingvariations thereof.

I claim:

1. Apparatus for preparing a rotating work element for balanced rotationhaving in combination, a free bearing for supporting" the lower end ofan element while spinning in a vertical position, driving means forrotating the element spinning freely upon said free-bearing, guide meansfor limiting the free movement of said element so that its position willbe within a predetermined range while it rotates upon a self-selectedaxis, and adjustable metal-removing means for engaging the portions ofsaid freely spinning element to be journalled to form bearing surfacesthereon concentric with the self-selected axisof rotation while theelement is spinning.

2. Apparatus for preparing a rotating work piece for balanced rotationhaving in combination, free bearing means for supporting the lower endof the work piece while spinning in a vertical position, means forrotating the work piece spinning freely upon said free bearing means,guide means for softly limiting the free movement of said work piecewithin a'predetermined range while it rotates freely upon aself-selected axis, a support member, bracket means slidably mountingsaid support member substantially horizontally with one end extendingtoward the position of a free spinning work piece, a cutting wheel andmeans for rotatively supporting and driving said wheel on said supportmember for movement toward or away from a work piece spinning on saidfree bearing means.

3. Apparatus for preparing a rotating work element'for balanced rotationhaving in combination, a substantially closed housing disposed.vertically, a free bearing disposed substantially axially at the lowerend .of said housing for supporting the lower end of a work elementwhile spinning-in a vertical position, driving means for rotating theelement spinning freely upon said free bearing, guide means supportedfrom said housing for softly guiding the free move ments of said'elementso that its position will be within a predetermined range while itrotates freely upon aself-selected axis, and metal-removing meansadjustably supported from said housing for engaging the portions of thefreely spinning element to be journalled to form bearing surfacesthereon concentric with the selfselected axis of rotation.

' 4. Apparatus for preparing a rotatingelement for balanced rotationhaving in combination, free bearing means for supporting the lower endof an element while spinning in a vertical position, vertical supportmeans spaced on op posite sides of said bearing means, means forrotating the element spinning freely upon said free bearing means, fluidprojecting means supported from said vertical support means and disposedto project fluid for softly guiding the free movement of said element sothat its position will be within a predetermined range while it rotatesfreely upon a self-selected axis, a support member mounted slidably insaid vertical support means in a-substantially horizontal position withone end extending inwardly toward the position of a free spinningelement, a cutting wheel, and means for rotatively supporting anddriving said wheel mounted on the inwardly extending end of said supportmember.

for movement toward or away from a freely spinning element to formbearing surfaces thereon.

CLARE F. SALTZ.

